The search field as well as all search results heavily jump around while the page is loading. In my (@thiemowmde) personal experience this constantly leads to misclicks. The most common use case is this: All I want is to click the first search result as fast as possible, the moment it appears on the screen. But what I hit instead are some fields in the advanced search form, because they pop up in the exact position where the first search result was just shown. The side-by-side comparison illustrates this:
Compare to the new recent changes as well as watchlist filters. Such jumps don't happen there. Instead a large empty area is reserved where the form does appear a moment later. The content below does not change position.